Adding larger PVs to a VG - Aix

This is a discussion on Adding larger PVs to a VG - Aix ; I have a "normal" VG (created on AIX5.1) with six 18.2 GB disks and only one
LV (plus the loglv) mirrored across two triplets. The PP size is 32 MB. Of the
three disks two has no Free PPs. We ...

Adding larger PVs to a VG

I have a "normal" VG (created on AIX5.1) with six 18.2 GB disks and only one
LV (plus the loglv) mirrored across two triplets. The PP size is 32 MB. Of the
three disks two has no Free PPs. We have AIX5.3 now.

I intend to extend the VG with six 36.4 GB disks, and if I do nothing else,
the MAX PPs per PV remains 1016, thus I'll end up losing about 2 GB/PV - which
I'd like to avoid.

One way to solve this problem would be to change the VG from "normal" to
"scalable" ('-G') and increase the MAX PPs per VG from 32K to 64K (-P'64');
however, according to the man pages, for this to work every PV in the VG have
to have enough free partitions to accomodate the VGDA expansion, and two of
ours are already full.

My question for you LVM experts is whether my goal (of not losing PPs on the
larger PVs) is achievable without recreating the VG (and restoring the data),
that is, on a live system?

Thanks a lot!

Re: Adding larger PVs to a VG

Since the PP size cannot be changed, the number of PPs can be increased
to 2032 using chvg with an option of -t 2. with this the max size of PV
that can be accomodated will be 63.5 GB, given the PP size of 32 MB.

HTH

Bela wrote:
> I have a "normal" VG (created on AIX5.1) with six 18.2 GB disks and only one
> LV (plus the loglv) mirrored across two triplets. The PP size is 32 MB. Of the
> three disks two has no Free PPs. We have AIX5.3 now.
>
> I intend to extend the VG with six 36.4 GB disks, and if I do nothing else,
> the MAX PPs per PV remains 1016, thus I'll end up losing about 2 GB/PV - which
> I'd like to avoid.
>
> One way to solve this problem would be to change the VG from "normal" to
> "scalable" ('-G') and increase the MAX PPs per VG from 32K to 64K (-P'64');
> however, according to the man pages, for this to work every PV in the VG have
> to have enough free partitions to accomodate the VGDA expansion, and two of
> ours are already full.
>
> My question for you LVM experts is whether my goal (of not losing PPs on the
> larger PVs) is achievable without recreating the VG (and restoring the data),
> that is, on a live system?
>
> Thanks a lot!

Re: Adding larger PVs to a VG

> > My question for you LVM experts is whether my goal (of not losing PPs on the
> > larger PVs) is achievable without recreating the VG (and restoring the data),
> > that is, on a live system?

or migrate some data off of your full disks to free up some space ..

Re: Adding larger PVs to a VG

Ashok Sangra wrote:
AS> Since the PP size cannot be changed, the number of PPs can be increased
AS> to 2032 using chvg with an option of -t 2. with this the max size of PV
AS> that can be accomodated will be 63.5 GB, given the PP size of 32 MB.
AS>
AS> HTH
AS>
AS> Bela wrote:
>> I have a "normal" VG (created on AIX5.1) with six 18.2 GB disks and only one
>> LV (plus the loglv) mirrored across two triplets. The PP size is 32 MB. Of the
>> three disks two has no Free PPs. We have AIX5.3 now.
>>
>> I intend to extend the VG with six 36.4 GB disks, and if I do nothing else,
>> the MAX PPs per PV remains 1016, thus I'll end up losing about 2 GB/PV
>>
>>

Re: Adding larger PVs to a VG

Mark Taylor wrote:
>> > My question for you LVM experts is whether my goal (of not losing PPs on the
>> > larger PVs) is achievable without recreating the VG (and restoring the data),
>> > that is, on a live system?
MT>
MT> or migrate some data off of your full disks to free up some space ..
MT>

Thanks Mark!
I've thought about that, but because I am being lazy I'll take the 'chvg -t2 VG'
route as pointed out by Ashok Sangra. It's also in the man pages... duh!

Re: Adding larger PVs to a VG

Ashok Sangra wrote:
> Bela wrote:
> > I have a "normal" VG (created on AIX5.1) with six 18.2 GB disks and only one
> > LV (plus the loglv) mirrored across two triplets. The PP size is 32 MB. Of the
> > three disks two has no Free PPs. We have AIX5.3 now.
> >
> > I intend to extend the VG with six 36.4 GB disks, and if I do nothing else,
> > the MAX PPs per PV remains 1016, thus I'll end up losing about 2 GB/PV - which
> > I'd like to avoid.
> >
> > One way to solve this problem would be to change the VG from "normal" to
> > "scalable" ('-G') and increase the MAX PPs per VG from 32K to 64K (-P'64');
> > however, according to the man pages, for this to work every PV in the VG have
> > to have enough free partitions to accomodate the VGDA expansion, and two of
> > ours are already full.
> >
> > My question for you LVM experts is whether my goal (of not losing PPs on the
> > larger PVs) is achievable without recreating the VG (and restoring the data),
> > that is, on a live system?
> >
> > Thanks a lot!
> Since the PP size cannot be changed, the number of PPs can be increased
> to 2032 using chvg with an option of -t 2. with this the max size of PV
> that can be accomodated will be 63.5 GB, given the PP size of 32 MB.

Just be aware that this halves the maximum number of PVs you can have in the
volume group. In a standard volume group, it means you can now have a max
of 16 PVs in the vg.

Regards,
Greg

Re: Adding larger PVs to a VG

Gregory Young wrote:
GY> Ashok Sangra wrote:
>> Bela wrote:
>> > I have a "normal" VG (created on AIX5.1) with six 18.2 GB disks and only one
>> > LV (plus the loglv) mirrored across two triplets. The PP size is 32 MB. Of the
>> > three disks two has no Free PPs. We have AIX5.3 now.
>> >
>> > I intend to extend the VG with six 36.4 GB disks, and if I do nothing else,
>> > the MAX PPs per PV remains 1016, thus I'll end up losing about 2 GB/PV
GY>
>> Since the PP size cannot be changed, the number of PPs can be increased
>> to 2032 using chvg with an option of -t 2. with this the max size of PV
>> that can be accomodated will be 63.5 GB, given the PP size of 32 MB.
GY>
GY> Just be aware that this halves the maximum number of PVs you can have in the
GY> volume group. In a standard volume group, it means you can now have a max
GY> of 16 PVs in the vg.
GY>
GY> Regards,
GY> Greg
GY>